Nitrous oxide is a gas with the chemical formula N2O. It is found naturally in the air. It is also made artificially, because it has many uses. It is a strong greenhouse gas, almost 300 times more so, per molecule, than carbon dioxide) and about one thousandth as plentiful. Because it is a greenhouse gas, people are trying to use it less.
Nitrous oxide is used by doctors and dentists to reduce pain. In the body, it makes people feel happy. For this reason it is also called "laughing gas". It is sometimes used only to feel happy, like an illegal drug.
Nitrous oxide is used in high performance cars to increase the power of their engines. When it is used this way, it is usually called "nitrous" or "NOS".